When it comes to mixing acoustic guitar, there is no “right” way to get the “right” sound. However, there are some big picture things to keep in mind that can really help you place this critical instrument in your mix.
Here are some of my favorite tips that I use on just about every mix. Treat them as starting points for your own music and see if they get you a bit closer to what you hear in your head.
Via irish10567 Flickr
Know The Acoustic’s Role
The very first thing you want to do when you begin to treat acoustic guitars in the mix is determine what their role is for song in question. Are the acoustic guitars a rhythmic suppliment to the rest of the band? If so then you likely need them to cut through and be “strummy” but not too full in the low mid range. If on the other hand the song is held together by a nice finger picking acoustic guitar then you likely will implement different EQ moves to keep it sounding full.
Knowing what role the acoustics play in your song helps you know which approach to take with EQ, compression, and panning. Before jumping in to mixing rules of thumb you need to have vision for the instrument. Otherwise the best advice in the world will be give you the worst results in your mix.
High Pass Filter
Your absolute best friend on acoustic guitars (or any guitar really) is the good ole’ high pass filter. Also known as a low cut, this simple EQ move gently rolls off the low end of your mix and let’s the high frequencies pass through unaffected. In practice you might not notice much of a sonic difference as you roll that high pass filter up to the 100Hz range. But in reality it is doing three things.
First it’s removing noise in the track. Any kind of low frequency hum or room noise captured when miking the acoustic will be removed which only cleans up the track. Secondly it frees up the low frequency spectrum in your mix for more important instruments down there like the bass guitar and kick drum (assuming there is one). And thirdly, it frees up headroom in your overall mix, which is a good thing.
How high should you go? If the acoustic is a dominant instrument, then start around the 100Hz mark. This will leave plenty of warmth and fullness in the low mids while still keeping out the unwanted super low stuff. If the acoustic is only for texture and strumming in a dense mix, I tend to roll it up closer to the 200Hz and 300Hz range. It might sound thin in solo mode, but it’ll be perfect in the mix.
Slow Attack Compression
Acoustic guitars are very transient heavy (i.e. rhythmic) instruments. That’s part of what makes them so useful. They have the chordal tone of an electric guitar, but with the percussive nature of a drum kit. To capitalize on this and make them poke out a bit more in the mix I suggest using some light compression, specifically with a slow attack setting.
The slower the attack, the more the time is available for the transients to come through unaffected. This allows you to squeeze the acoustic a bit, and bring it up in perceived volume a tiny bit, all without squashing the most important part, the transient. This results in a more apparent and exciting guitar sound in the mix.
Be Careful With Stereo Acoustics
One final word of warning. If you are dealing with stereo recorded acoustic guitar tracks, spend some time making sure they are actually in phase. Collapse your mix to mono and see if the tone and fullness of the guitars goes away. If so, you might need to zoom into the waveforms and do some aligning.
One of the saddest things that can happen is that you have a nice sounding (seemingly) stereo acoustic guitar track in your mix when listening in stereo, but in mono (i.e. just about everywhere else except for in headphones) they become thin and harsh. This is why I usually avoid stereo guitars in the first place. But if you have them, make sure they are phase coherent in mono, not just in stereo.